Again: If the action were not situated far below the surface of the earth, the mountains, which only serve as _chimnies_, and which have been formed by the action of the volcanos, _would sink in_. This has been the case in a few instances. This will appear more clearly if we consider the _amount_ of matter ejected. Did it not come from an immeasurable distance beneath, the accumulated mass at the surface of the earth would break down the _substrata_ which lie over the immense caverns formed by the ejection. The _dimensions_ of those caverns, situated under the volcanic mountains, are far greater than one would suppose at first consideration. _The internal caverns must be as large as the ejected masses, which came out of them._ Ætna is known to have thrown out matter sufficient to form twenty such mountains as it is. It is strongly probable that the whole island of Sicily is of volcanic origin. Humboldt says the dome-shaped craters of volcanos rise from six hundred to eighteen thousand feet in height. He considers the _whole mountainous district of Quito as one immense volcano_. Indeed, from a close survey of the geological features of the earth, there is reason to believe, that at very remote periods almost the whole surface of our globe has been the theatre of volcanic action. It is a matter of gratitude that its amount is growing less every year, of course the destructions by earthquakes are more limited. In process of time, it may be hoped, the earth may become permanently tranquil, nor flame, nor shake, until the final catastrophe, which God has ordained to destroy our planet, by a general and simultaneous action of all the fires of the earth. P.S. It may be of advantage to recollect, that the _expansive force of steam is to that of gunpowder as 140 to 5_. According to Vauban, 140 pounds of water converted into vapor would produce an explosion capable of blowing up 77,000 pounds, while 140 pounds of gunpowder could only blow up a mass of 30,000. _See the text under the head_, “SALUTARY EFFECTS OF WATER.” APPENDIX. _On the temperature of the earth anciently._ That the temperature of the earth’s surface was much higher in the first ages of its existence, than since the period of authentic history, seems now to be nearly established, in the opinion of the learned, and only requires time to have the weight of evidence produce its proper effect on the great mass of community. Though this fact would be apprehended from what is said above, it may be desirable to the reader to see a concise view of the reasons which induce this opinion.